US3666826A - Purification of hydrodealkylation reaction vent hydrogen - Google Patents

Purification of hydrodealkylation reaction vent hydrogen Download PDF

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Publication number
US3666826A
US3666826A US101321A US3666826DA US3666826A US 3666826 A US3666826 A US 3666826A US 101321 A US101321 A US 101321A US 3666826D A US3666826D A US 3666826DA US 3666826 A US3666826 A US 3666826A
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United States
Prior art keywords
benzene
hydrogen
toluene
liquid
feed
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US101321A
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English (en)
Inventor
Bernard I Newberger
Stanley W Ehrlich
Manuel N Vergara
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BERNARD I NEWBERGER
MANUEL N VERGARA
STANLEY W EHRLICH
HRI Inc
Original Assignee
BERNARD I NEWBERGER
MANUEL N VERGARA
STANLEY W EHRLICH
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Assigned to HRI, INC., A DE CORP. reassignment HRI, INC., A DE CORP. ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: HYDROCARBON RESEARCH, INC.
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C15/00—Cyclic hydrocarbons containing only six-membered aromatic rings as cyclic parts
    • C07C15/02—Monocyclic hydrocarbons
    • C07C15/04—Benzene
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C4/00—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms
    • C07C4/08—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by splitting-off an aliphatic or cycloaliphatic part from the molecule
    • C07C4/12—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by splitting-off an aliphatic or cycloaliphatic part from the molecule from hydrocarbons containing a six-membered aromatic ring, e.g. propyltoluene to vinyltoluene
    • C07C4/14—Preparation of hydrocarbons from hydrocarbons containing a larger number of carbon atoms by splitting-off an aliphatic or cycloaliphatic part from the molecule from hydrocarbons containing a six-membered aromatic ring, e.g. propyltoluene to vinyltoluene splitting taking place at an aromatic-aliphatic bond
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C7/00—Purification; Separation; Use of additives
    • C07C7/005—Processes comprising at least two steps in series
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S585/00—Chemistry of hydrocarbon compounds
    • Y10S585/8995—Catalyst and recycle considerations
    • Y10S585/901—Catalyst and recycle considerations with recycle, rehabilitation, or preservation of solvent, diluent, or mass action agent

Definitions

  • This vapor contains a substantial amount of benzene.
  • the exact amount is a function of the amount of net effluent gas as well as the temperatures and pressure of the effluent flash drum.
  • the benzene in this effluent can be in the range from 2-10 percent of the total benzene production. It is, therefore, essential to the efficiency of the overall process that this benzene be recovered.
  • the aromatics content in the vent hydrogen is about 1 to 1% volume percent and is comprised mainly of benzene and toluene in ratios between 5:1 to 20:1.
  • the ratio of toluene to benzene in the vent hydrogen is greater than 8:1 then the danger of freezing at purification temperatures of as low as 200 F is removed.
  • the net reactor effluent is flashed in a flash drum at a temperature between about 100 to 150 F and at a pressure between about 500 to 600 psig to produce a vapor and liquid stream.
  • the purpose of this flash is twofold.
  • liquid stream comprised mainly of product aromatics such as benzene or naphthalene and unconverted aromatic feed.
  • product aromatics such as benzene or naphthalene
  • the liquid stream has dissolved in it a small amount of light gases and saturated hydrocarbons resulting from the hydrodealkylation reactions, such as hydrogen, methane, ethane, propane, hydrogen sulfide, thiophene, etc. Some of these are removed in the stabilizer; and subsequent fractionation results in pure product.
  • a vapor stream containing about 55 percent hydrogen is formed.
  • the aromatics content is about 1 to 1% volume percent and is comprised mainly of benzene and toluene in a range from 5:1 to 20:1. It is undesirable to vent these aromatics because this represents an economic waste of valuable product and feed.
  • the high benzene to toluene ratio is also detrimental if a hydrogen purification unit is used to upgrade the purity of the vent gas.
  • An object of this invention is to minimize the loss of total aromatics in the vent hydrogen stream.
  • Another object of this invention is to control the ratio of toluene to benzene in the vent hydrogen stream without using an absorber.
  • the drawing is a schematic flow diagram of a hydrodealkylation process wherein the vent hydrogen stream enters a liquid vapor equilibrium staging process for purification.
  • Toluene or mixed alkylated aromatic hydrocarbons are suitable as feed material.
  • Toluene is the most preferred feed while mixed alkylated aromatics containing considerable toluene is less preferred and mixed alkylated aromatics containing no toluene is least preferred.
  • the above feeds in order to be suitable, must contain less than about 1 percent benzene but may contain some saturated non-aromatics. Diolefins and olefins contained in the feed must be removed to make a feed suitable for use in the hydrodealkylation system and it is desirable to minimize the thiophenic sulfur in the feed stream. Such treatment steps are not shown in this system as the most preferred feed is a toluene feed.
  • the combined hydrogen and feed in line 39 is mixed with recycle hydrogen in line 83 and rich oil in 28 and is heated at 40 by exchange against reactor effluent. At this point a stream 65 from the stabilizer 60 is added and the total reactor feed is heated to about 1,200 F in fired heater 42. It then enters the reactor 44.
  • the reactor 44 is an internally insulated open chamber containing no catalytic surfaces.
  • the pressure in this reactor is maintained at about 600 psig.
  • the reactor is so sized that the residence time of the total feed is in the range of about 20 to 40 seconds.
  • the temperature profile in the reactor is controlled by adding quench gas at appropriate points in the reactor such as 52.
  • the temperature profile is so controlled that it does not exceed 1,350 F at any point within the reactor. It is also controlled so that about 75 percent of the alkylated aromatic hydrocarbons in the total feed is converted.
  • the reactor effluent is quenched to about 1,200 F by liquid quench 56. While quenching in this manner is sufficient to stop the reactions which occur in the reactor 44, it does permit reactions to take place which produce certain hydrocarbon impurities which form azeotropic boiling mixtures with benzene.
  • the reactor effluent 46 is then cooled by exchange against reactor feed at 40, by exchange against stabilizer feed at 47, and by water at 48. It is then separated into liquid and vapor in flash chamber 50. Part of the flashed vapor in 51 is passed through compressor 20 and is used to quench the reactor at 52 and also to supply recycle hydrogen for control of the hydrogen to aromatics ratio at the inlet to the reactor via line 83. The net vapor is taken at 53 and cooled to about F in exchanger 54 by exchange against the liquid in 28 from the two stage flash drum 34 and the vapor from 34 in line 35. If the hydrogen in line 35 is to be passed to a hydrogen purification unit it would not pass through heat exchanger 54 but it would go directly to the hydrogen purification unit.
  • the cooled vent hydrogen stream in 57 combines with the feed from line 19 or recycle aromatics in 37 before undergoing further cooling to about 65 F in 22.
  • the cooled mixture now passes in 25 to the first stage of 34 where it undergoes a flashing to produce a liquid stream containing about to 20 percent benzene in 31 and a vapor stream which contains 0.2 to 0.6 percent aromatics in 21 with a toluene to benzene ratio of about 2 to l.
  • the vapor in 21 combines with feed from 16 or recycle aromatics in 84 to pass through line 23 to the second flashing stage at 34.
  • the second stage there is a flashing of the mixture to provide a liquid stream in 27 which combines with the first stage liquid to leave in 31.
  • the vapor effluent from the second stage of 34 in 35 contains about 0.2 to 0.5 percent aromatics with a toluene to benzene ratio of about 1 l to 1.
  • Part of the liquid from flash chamber 50 is taken through line 56 and used to quench the reactor effluent at 55.
  • the net liquid from 50 passes through and is reduced in. pressure through valve 59 and is heated at 47 by exchange against reactor efiluent and then goes by 58 to the stabilizer 60. Ifrecycle aromatics in 37 and 84 are used as the contacting liquids and an additional quantity of this material is required, then the net liquid at 50, after reduction in pressure, is combined with rich oil in 32.
  • the bottoms from the stabilizer 60 are taken at 66 as feed to the clay tower 68.
  • the operating pressure of the stabilizer 60 is maintained at that necessary to give a bottoms temperature of about 425 F. This enables the bottoms 66 to go directly to the clay tower without intermediate heating.
  • the stabilizer is furnished with a reboiler 64.
  • the clay tower effluent 69 goes directly to the benzene tower 70.
  • This is a conventional fractionator operating at essentially atmospheric pressure and reboiled at 76.
  • High purity benzene product is taken as the overhead product at 72.
  • the bottoms 74 are preferably sent by line 77 to the recycle tower at 78.
  • the bottoms containing the recycle aromatics are sent directly back to the reactor through line 75.
  • the recycle tower 78 is run at atmospheric pressure.
  • the overhead 79 is essentially rich in alkylated aromatics primarily toluene with recycle diphenyl and water vapor.
  • the overhead in 79 passes through condenser 81 and separator 85 with the water removed in 86.
  • a portion of the toluene and recycle diphenyl is returned to 78 and the remainder is sent through line 80 to be used as recycle for the system.
  • the unconverted toluene can be returned to the reactor 44 through line 37 and 84.
  • the selection of bypasses 37 and 84 is dictated by the requirements in 34. If extra lean oil is desired in 34, bypasses 37 and 84 are used and all of line 80 is chilled and used as contacting liquid. If the demand in 34 is low, the unconverted toluene can be sent directly to the reactor via line 39 and in so doing, bypass 34. The rich oil in 31 is sent to the reactor in 28.
  • the excess rich oil in 32 is combined with the net liquid from the reactor effluent flash drum 50 and is sent directly to the stabilizer 60 and then to the benzene tower 70 and recycle tower 78 for removal of the light components and benzene that were recovered in 34.
  • hydrodealkylation operations are conducted in the temperature range of l,O00 to 1,500 F and temperature differences can be kept at 200 F or less.
  • the operating pressures are normally in the range of 400 to 800 psig with a reaction time within the period of 10 to 60 seconds.
  • a process for the hydrodealkylation of alkylated aromatic hydrocarbon feed which comprises the steps of:
  • reaction zone between about 1,000 P and about 1,500 F and a pressure between about 400 psig and about 800 psig;
  • step (e) contacting the hydrogen from step (e) with heavy hydrocarbons to shift the benzene-toluene equilibrium;
  • step (j) flashing the mixture to obtain a liquid phase of 5 to 15 percent benzene and a vapor phase of 0.2 to 0.5 percent aromatics with a toluene to benzene ratio from 2 to l to 15 to k. recovering the benzene as product from step (j).
  • step (j) has a toluene to benzene ratio of less than 8 to 1 6.
  • step (j) has a toluene to benzene ratio of greater than 8 to l and is fed to a hydrogen purification unit.

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Oil, Petroleum & Natural Gas (AREA)
  • Analytical Chemistry (AREA)
  • Water Supply & Treatment (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • General Chemical & Material Sciences (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
US101321A 1970-12-24 1970-12-24 Purification of hydrodealkylation reaction vent hydrogen Expired - Lifetime US3666826A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US10132170A 1970-12-24 1970-12-24

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US3666826A true US3666826A (en) 1972-05-30

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Country Status (6)

Country Link
US (1) US3666826A (online.php)
CA (1) CA954535A (online.php)
ES (1) ES392324A1 (online.php)
FR (1) FR2126989B1 (online.php)
GB (1) GB1322289A (online.php)
IT (1) IT953201B (online.php)

Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3188359A (en) * 1962-03-01 1965-06-08 Pullman Inc Non-catalytic dealkylation of alkyl substituted benzene-ring compounds
US3213151A (en) * 1962-07-27 1965-10-19 Phillips Petroleum Co Recovery of hydrogen from gaseous mixtures and improved hydrogenation process
US3260765A (en) * 1965-05-25 1966-07-12 Universal Oil Prod Co Treatment of alkyl-substituted aromatic compounds
US3287431A (en) * 1965-09-13 1966-11-22 Atlantic Refining Co Hydrodealkylation with azeotrope recycle
US3291849A (en) * 1964-11-16 1966-12-13 Hydrocarbon Research Inc Hydrodealkylation

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3188359A (en) * 1962-03-01 1965-06-08 Pullman Inc Non-catalytic dealkylation of alkyl substituted benzene-ring compounds
US3213151A (en) * 1962-07-27 1965-10-19 Phillips Petroleum Co Recovery of hydrogen from gaseous mixtures and improved hydrogenation process
US3291849A (en) * 1964-11-16 1966-12-13 Hydrocarbon Research Inc Hydrodealkylation
US3260765A (en) * 1965-05-25 1966-07-12 Universal Oil Prod Co Treatment of alkyl-substituted aromatic compounds
US3287431A (en) * 1965-09-13 1966-11-22 Atlantic Refining Co Hydrodealkylation with azeotrope recycle

Also Published As

Publication number Publication date
IT953201B (it) 1973-08-10
CA954535A (en) 1974-09-10
GB1322289A (en) 1973-07-04
FR2126989B1 (online.php) 1973-06-08
ES392324A1 (es) 1973-08-16
FR2126989A1 (online.php) 1972-10-13

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AS Assignment

Owner name: HRI, INC., 1313 DOLLEY MADISON BLVD, MC LEANN, VA.

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:HYDROCARBON RESEARCH, INC.;REEL/FRAME:004180/0621

Effective date: 19830331